1. Field of the Invention
This invention relates to an optical device, an image display apparatus and a head-mounted display unit.
2. Description of the Related Art
A virtual image display apparatus or image display apparatus is known and disclosed, for example, in JP-T-2005-521099 or Japanese Patent Laid-Open No. 2006-162767. In the virtual image display apparatus, a two-dimensional image formed by an image forming apparatus is expanded by a virtual image optical system such that it is observed as an enlarged virtual image by an observer.
A virtual image display apparatus of the type described is schematically shown in FIG. 10. Referring to FIG. 10, the image display apparatus 200 shown includes an image forming apparatus 201 including a plurality of pixels arrayed in a two-dimensional matrix, and a collimate optical system 202 for converting light emitted from the pixels of the image forming apparatus 201 into parallel light. The image display apparatus 200 further includes light guide means 203 which receives parallel light from the collimate optical system 202, guides the parallel light therein and emits the parallel light therefrom. The light guide means 203 includes a light guide plate 204 from which incident light is emitted after it propagates by total reflection in the inside of the light guide plate 204. The light guide means 203 further includes first deflection means 205 formed, for example, from a single layer of a light reflecting film for reflecting light incident to the light guide plate 204 so that the light is reflected totally in the inside of the light guide plate 204. The light guide section 203 further includes second deflection means 206 formed, for example, from a light reflecting multilayer film having a multilayer lamination structure for emitting light propagated by total reflection in the inside of the light guide plate 204 from the light guide plate 204. If the image display apparatus 200 having such a configuration as just described is used to configure, for example, a head-mounted display (HD) unit, then the unit can be formed in a light-weighted small-sized form.